Acta Crystallographica Section B

Structural Science

Volume 59, Part 6 (December 2003)

Cover illustration: Orange polytypically disordered crystals of HgI2 are built from layers of corner-linked Hg4I10 supertetrahedra. The stacking disorder has been quantitatively analyzed with a Markov chain model. Two probabilities describing next-nearest-layer interactions were adjusted to observed diffuse intensity profiles extracted from image-plate detector data. Results show nearly equal volumes of the two maximum degree of order structures, with an average domain thickness of about 5 layers or 30 Å [Hostettler, Birkedal & Schwarzenbach (2002), Acta Cryst. B58, 903-913].

• research papers
• addenda and errata

research papers

Acta Cryst. (2003). B59, 687-700  [ doi:10.1107/S0108768103017075 ] Characterization of intra-framework and guest/host interactions in the AlPO4-15 molecular sieve by charge-density analysis E. Aubert, F. Porcher, M. Souhassou and C. Lecomte Synopsis: An accurate charge-density analysis of the title compound is presented and compared with the procrystal topological properties. Online 25 November 2003

Acta Cryst. (2003). B59, 701-708  [ doi:10.1107/S0108768103021761 ] Structural refinements of high-pressure phases in germanium dioxide K. Shiraki, T. Tsuchiya and S. Ono Synopsis: Rietveld refinements of the high-pressure polymorphs of GeO2 synthesized in the laboratory have been performed. The structure refinements confirm that the high-pressure phases have the -PbO2- and pyrite-type (modified-fluorite-type) structures. Online 25 November 2003

Acta Cryst. (2003). B59, 709-719  [ doi:10.1107/S0108768103022213 ] Two-dimensionally modulated structure of the rare-earth polysulfide GdS2-x (x = 0.18 13/72) R. Tamazyan, S. van Smaalen, I. G. Vasilyeva and H. Arnold Synopsis: GdS forms a 144-fold superstructure that is shown to result from an ordering of vacancies in the layers of S atoms. Charge balance is maintained by the presence of both S dimers and S ions in these layers. Online 25 November 2003

Acta Cryst. (2003). B59, 720-729  [ doi:10.1107/S0108768103019694 ] Structure of 1-CoZn7.8, an example of a phason pinning-unpinning transformation? H. Lind, M. Boström, V. Petrícek and S. Lidin Synopsis: The incommensurately (3 + 1)-dimensional modulated structure of 1-CoZn7.8 was solved and refined from single-crystal X-ray diffraction data. The linking of double icosahedra along the b axis is considered to be both a consequence of geometric demands and the cause of the incommensurate modulation. Online 25 November 2003

Acta Cryst. (2003). B59, 730-746  [ doi:10.1107/S0108768103022018 ] Single-crystal structure refinement of NaTiSi2O6 clinopyroxene at low temperatures (298 < T < 100 K) G. J. Redhammer, H. Ohashi and G. Roth Synopsis: The alkali-metal clinopyroxene compound NaTiSi2O6 (sodium titanium silicate) shows a crystallographic phase transition at 197 K. The structure of the low-temperature phase was determined and the temperature-induced structural changes were investigated in detail by X-ray diffraction experiments on a single crystal between 100 and 298 K. Online 25 November 2003

Acta Cryst. (2003). B59, 747-752  [ doi:10.1107/S0108768103023437 ] Low-temperature structure of V6O13 J. Höwing, T. Gustafsson and J. O. Thomas Synopsis: The low-temperature structure of V6O13 has been re-investigated using single-crystal X-ray diffraction. The transition temperature and heat of transition have been determined using differential scanning calorimetry. Online 25 November 2003

Acta Cryst. (2003). B59, 753-759  [ doi:10.1107/S0108768103022602 ] Structures of potassium, sodium and lithium bis(oxalato)borate salts from powder diffraction data P. Y. Zavalij, S. Yang and M. S. Whittingham Synopsis: The ab initio determinations of the crystal structures of three alkali-metal salts A[B(C2O4)2] (A = K, Na, Li) from conventional powder diffraction data are reported. Online 25 November 2003

Acta Cryst. (2003). B59, 760-769  [ doi:10.1107/S0108768103021505 ] Diffuse X-ray scattering from 4,4'-dimethoxybenzil, C16H14O4: analysis via automatic refinement of a Monte Carlo model T. R. Welberry and A. P. Heerdegen Synopsis: A recently developed method for fitting a Monte Carlo computer-simulation model to observed single-crystal diffuse X-ray scattering has been used to study diffuse scattering in 4,4'-dimethoxybenzil, C16H14O4. The analysis has shown that the most prominent features of the diffraction patterns, diffuse steaks that occur normal to the direction, are due to longitudinal displacement correlations along chains of molecules extending in this direction. Online 25 November 2003

Acta Cryst. (2003). B59, 770-778  [ doi:10.1107/S0108768103021013 ] Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal F. Blockhuys, C. M. L. Vande Velde, S. T. Maes, C. Peten, H. J. Geise, C. Van Alsenoy and A. T. H. Lenstra Synopsis: Static disorder in the crystal structure of E-1,2-bis(3-methoxy-2-thienyl)ethene is described and attributed to a high-energy conformer of the compound. Online 25 November 2003

Acta Cryst. (2003). B59, 779-786  [ doi:10.1107/S0108768103023255 ] Monitoring structural transformations in crystals. 6. The [4 + 4] photodimerization of 9-methylanthracene I. Turowska-Tyrk and E. Trzop Synopsis: The structural changes in a crystal of 9-methylanthracene during the [4 + 4] photodimerization were monitored step-by-step by means of X-ray structure analysis. The results were compared with data for the [2 + 2] photodimerization. Online 25 November 2003

Acta Cryst. (2003). B59, 787-793  [ doi:10.1107/S0108768103022729 ] Protonation site and hydrogen bonding in anhydrous and hydrated crystalline forms of doxazosin mesylate from powder data V. V. Chernyshev, D. Machon, A. N. Fitch, S. A. Zaitsev, A. V. Yatsenko, A. N. Shmakov and H.-P. Weber Synopsis: The protonation site and hydrogen bonding in an anhydrous and in a hydrated crystalline form of doxazosin mesylate, a commonly used antihypertensive medication, have been determined as a result of crystal structure solution from synchrotron X-ray powder diffraction data. Online 25 November 2003

Acta Cryst. (2003). B59, 794-801  [ doi:10.1107/S0108768103024984 ] Variable-temperature neutron diffraction studies of the short, strong NO hydrogen bonds in the 1:2 co-crystal of benzene-1,2,4,5-tetracarboxylic acid and 4,4'-bipyridyl J. A. Cowan, J. A. K. Howard, G. J. McIntyre, S.M.-F. Lo and I. D. Williams Synopsis: The 1:2 adduct of benzene-1,2,4,5-tetracarboxylic acid and 4,4'-bipyridyl has been studied by single-crystal neutron diffraction at 20, 200 and 296 K. The structure contains two short NO hydrogen bonds; the H atom in the shortest is observed to migrate across the hydrogen bond between 20 and 296 K. Online 25 November 2003

Acta Cryst. (2003). B59, 802-810  [ doi:10.1107/S010876810302411X ] New electron diffraction method to identify the chirality of enantiomorphic crystals H. Inui, A. Fujii, K. Tanaka, H. Sakamoto and K. Ishizuka Synopsis: A new CBED (convergent-beam electron diffraction) method is proposed for the identification of the chirality of enantiomorphic crystals, in which asymmetry in the intensities of the reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of a computer-simulated CBED pattern. With the present method, a single CBED pattern is sufficient and chiral identification can be made for all the possible enantiomorphic crystals that are allowed to exist in crystallography. Online 25 November 2003

addenda and errata

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